Identifying unit for working machine and pressure apparatus

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a working machine such as a chip mounter designed to mount an electronic circuit chip onto a printed wiring board. In particular, the invention relates to an identifying unit and a pressure apparatus utilized in the working machine.

2. Description of the Prior Art

A chip mounter is well known as disclosed in Japanese Patent Application Publication No. 2004-55705, for example. The chip mounter includes a working head opposed to the surface of a work stage. A movable member is designed to move toward and away from the surface of the work stage in the chip mounter. The movable member is supported on a guide for relative movement. A load cell is fixed to the movable member. The working head is detachably coupled to the load cell. When the working head is urged against a printed circuit board on the work stage, the applied load is measured at the load cell.

Various working heads are prepared for the chip mounter depending on the purposes. Control parameters may be selected for the individual working heads in the chip mounter. The control parameters are employed in controlling the position of the movable member and the thrust of the movable member. Bar codes are heretofore employed to identify the working head in setting the control parameters, for example. When the bar code is erroneously detected in the chip mounter, the control parameters cannot correctly be set for the working head on the movable member in the chip mounter.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide an identifying unit and a working machine reliably contributing to an accurate identification of a working head. It is an object of the present invention to provide a pressure apparatus contributing to realization of the working machine.

According to a first aspect of the present invention, there is provided an identifying unit for a working machine, comprising: a force sensor detachably supporting a working head; and a controller circuit designed to identify the working head based on load detected at the force sensor.

When the working head is replaced with another one, for example, the load changes in the force sensor in the identifying unit. In general, the individual working head has the specific weight. The working heads can thus be differentiated from each other based on the weight. Accordingly, the controller circuit is allowed to reliably identify the working head after the replacement with a higher accuracy based on the detected load.

According to a second aspect of the present invention, there is provided a pressure apparatus comprising: a movable member; a force sensor coupled to the movable member; a contact member detachably connected to the force sensor; a drive source connected to the movable member for generating a driving force to drive the movable member; and a controller circuit connected to the force sensor and the drive source so as to control the drive source based on load detected at the force sensor, said controller circuit designed to identify the contact member based on the load detected at the force sensor.

When the contact member is replaced with another one, for example, the load changes in the force sensor in the pressure apparatus in the same manner as described above. In general, the individual contact member has the specific weight. The contact members can thus be differentiated from each other based on the weight. Accordingly, the controller circuit is allowed to reliably identify the contact member after the replacement with a higher accuracy based on the detected load.

In addition, the force sensor is utilized to identify the contact member. The force sensor is often originally employed in the pressure apparatus. It is not necessary to add a component such as a sensor peculiar to the identification of the contact member into the pressure apparatus. The invention can be applied to a conventional pressure apparatus without any difficulty.

The controller circuit may set a control parameter of the contact member based on the identification of the contact member. Automatic setting of the control parameter in response to the identification of the contact member enables reduction in troublesome operations in replacement of the contact members. Since the contact member can be identified with a higher accuracy as described above, an erroneous setting of the control parameter can reliably be avoided in the pressure apparatus.

According to a third aspect of the present invention, there is provided a working machine comprising: a work table defining the surface along a horizontal plane; a working head opposed to the surface of the work table; a force sensor detachably supporting the working head; a movable member coupled to the force sensor; a drive source connected to the movable member for generating a driving force to drive the movable member; and a controller circuit connected to the force sensor and the drive source so as to control the drive source based on load detected at the force sensor, said controller circuit designed to identify the contact member based on the load detected at the force sensor.

When the working head is replaced with another one, for example, the load changes in the force sensor in the working machine in the same manner as described above. In general, the individual working head has the specific weight. The working heads can thus be differentiated from each other based on the weight. Accordingly, the controller circuit is allowed to reliably identify the working head after the replacement with a higher accuracy based on the detected load. In addition, the force sensor is utilized to identify the working head. The force sensor is often originally employed to effect processing such as a pressing operation in the working machine. It is not necessary to add a component such as a sensor peculiar to the identification of the contact member into the working machine. The invention can be applied to a conventional working machine without any difficulty.

The controller circuit may set a control parameter of the working head based on the identification of the working head. Automatic setting of the control parameter in response to the identification of the working head enables reduction in troublesome operations in replacement of the working heads. Since the working head can be identified with a higher accuracy as described above, an erroneous setting of the control parameter can reliably be avoided in the working machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiment in conjunction with the accompanying drawings, wherein:

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view schematically illustrating the structure of a chip mounter according to a specific example of the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is a sectional view schematically illustrating the structure of a force sensor in the chip mounter;

<figref idref="DRAWINGS">FIG. 3</figref> is a flowchart illustrating processings according to execution of a software program in replacement of ultrasonic heads in the chip mounter; and

<figref idref="DRAWINGS">FIG. 4</figref> is a flowchart illustrating processings according to execution of a software program in replacement of ultrasonic heads in the chip mounter.

DESCRIPTION OF THE PREFERRED EMBODIMENT

<figref idref="DRAWINGS">FIG. 1</figref> schematically illustrates the structure of a chip mounter <b>11</b> as a specific example of a working machine according to the present invention. The chip mounter <b>11</b> includes a work table <b>12</b> defining a top surface along a horizontal plane. The work table <b>12</b> is allowed to move in a horizontal direction. A printed circuit board or printed wiring board may be mounted on the top surface of the work table <b>12</b>.

Here, a three dimensional coordinate system or xyz-coordinate system is set in the chip mounter <b>11</b>. The xyz-coordinate system includes the y-axis perpendicular to the top surface of the work table <b>12</b>, namely the horizontal plane. The work table <b>12</b> can be moved in the x-axis and the y-axis. The position of the work table <b>12</b> can be determined based on the x-axis and y-axis of the xyz-coordinate system.

A pressure apparatus <b>13</b> is related to the work table <b>12</b>. The pressure apparatus <b>13</b> includes an ultrasonic head <b>14</b> as an example of a contact member or a working head according to the present invention. The ultrasonic head <b>14</b> is designed to support an electronic circuit chip at the tip end. An ultrasonic oscillator is installed within the ultrasonic head <b>14</b> so as to generate an ultrasonic vibration of the ultrasonic head <b>14</b>. The ultrasonic oscillator transmits the ultrasonic wave to the electronic circuit chip. The ultrasonic wave serves to vibrate the ultrasonic head <b>14</b> in parallel with the horizontal plane.

The ultrasonic head <b>14</b> is designed to move in the perpendicular direction perpendicular to the top surface of the work table <b>12</b> as described later in detail. The perpendicular movement of the ultrasonic head <b>14</b> serves to urge the electronic circuit chip against the printed circuit board held on the top surface of the work table <b>12</b>. The ultrasonic vibration is in this manner transmitted to the electronic circuit chip. Ultrasonic bonding can be achieved based on the action of the ultrasonic head <b>14</b>.

The pressure apparatus <b>13</b> includes a movable member <b>15</b> coupled to the ultrasonic head <b>14</b>. A force sensor <b>16</b> is interposed between the ultrasonic head <b>14</b> and the movable member <b>15</b>. The force sensor <b>16</b> detachably holds the ultrasonic head <b>14</b>. The force sensor <b>16</b> is designed to detect the force or load applied to the ultrasonic head <b>14</b> along the y-axis in the perpendicular direction. The force sensor <b>16</b> converts the detected load to an electric signal. The force sensor <b>16</b> will be described later in detail.

The pressure apparatus <b>13</b> further includes a support member <b>17</b>. The support member <b>17</b> supports the movable member <b>15</b>. The support member <b>17</b> stands stationary during the movement of the movable member <b>15</b>. Specifically, the ultrasonic head <b>14</b>, the moveable member <b>15</b> and the force sensor <b>16</b> are allowed to move relative to the support member <b>17</b>. A drive source such as a voice coil motor (VCM) <b>18</b> is coupled to the movable member <b>15</b>. The voice coil motor <b>18</b> serves to generate a driving force to drive the movable member <b>15</b>. The voice coil motor <b>18</b> induces a perpendicular movement of the ultrasonic head <b>14</b> and the force sensor <b>16</b>.

An image capturing apparatus <b>21</b> is related to the work table <b>12</b> and the pressure apparatus <b>13</b>. The image capturing apparatus <b>21</b> is allowed to move in the horizontal direction along the z-axis in parallel with the top surface of the work table <b>12</b>. The image capturing apparatus <b>21</b> includes a camera unit <b>22</b> designed to capture images. When the image capturing apparatus <b>21</b> moves in the horizontal direction in a specific manner, the camera unit <b>22</b> is positioned in a space between the ultrasonic head <b>14</b> and the top surface of the work table <b>12</b>. The camera unit <b>22</b> is in this manner capable of simultaneously capture the images of the electronic circuit chip held on the ultrasonic head <b>14</b> and the printed circuit board placed on the top surface of the work table <b>12</b>.

The chip mounter <b>11</b> includes a main controller circuit <b>23</b>. The main controller circuit <b>23</b> is designed to control the operation of the chip mounter <b>11</b> in accordance with a predetermined processing program. The main controller circuit <b>23</b> supplies a predetermined electric signal to the ultrasonic oscillator installed within the ultrasonic head <b>14</b>. Ultrasonic vibration is induced in the ultrasonic head <b>14</b> based on the supplied electric signal.

A pressure apparatus controlling circuit <b>24</b> is connected to the main controller circuit <b>23</b>. The pressure apparatus controlling circuit <b>24</b> includes a central processing unit (CPU) <b>25</b>. A random access memory (RAM) <b>26</b> and a non-volatile memory <b>27</b> are connected to the CPU <b>25</b>. A flash memory may be employed as the non-volatile memory <b>27</b>, for example. A software program <b>28</b> is stored in the non-volatile memory <b>27</b>. The CPU <b>25</b> executes the processings in accordance with the software program temporarily held within the random access memory <b>26</b>.

Here, the CPU <b>25</b> is designed to supply the voice coil motor <b>18</b> with electric current. The CPU <b>25</b> implements the software program <b>28</b> to supply the electric current. The perpendicular movement of the movable member <b>15</b> is induced based on the supplied current. The ultrasonic head <b>14</b> is in this manner moved along the y-axis in the perpendicular direction perpendicular to the top surface of the work table <b>12</b>. The CPU <b>25</b> controls the thrust applied to the ultrasonic head <b>14</b> as described later in detail. The force sensor <b>16</b> and the pressure apparatus controlling circuit <b>24</b> serves as an identifying unit according to the present invention.

A head data <b>29</b> is stored in the non-volatile memory <b>27</b>. The head data <b>29</b> is utilized to identify individual ultrasonic heads <b>14</b>. Here, the head data <b>29</b> includes a weight data specifying the weight of various working heads including the ultrasonic heads <b>14</b>. The CPU <b>25</b> obtains the load based on the electric signal supplied from the force sensor <b>16</b>. The CPU <b>25</b> is allowed to determine the weight of the ultrasonic head <b>14</b> based on the detected load. The CPU <b>25</b> thus identifies a specific ultrasonic head <b>14</b> based on the comparison between the head data <b>29</b> and the detected weight.

Control parameters <b>31</b> for the ultrasonic heads <b>14</b> are further stored in the non-volatile memory <b>27</b>. The control parameters <b>31</b> are uniquely set for the various working heads including the individual ultrasonic heads <b>14</b>. The control parameters <b>31</b> may include PID control gains, coefficients of filter, limits or thresholds for various numerical data, and the like. The PID control gains may be employed to control the position and thrust of the ultrasonic head <b>14</b>. The coefficients of filter may be employed to suppress an excessive vibration of the ultrasonic head <b>14</b>. The limits define the upper limit of the current value for current supplied to the ultrasonic head <b>14</b>, the upper limit for the load applied to the force sensor <b>16</b>, and the like.

A work table driving circuit <b>32</b> is connected to the main controller circuit <b>23</b>. The work table driving circuit <b>32</b> is designed to supply a predetermined electric signal to an electric motor incorporated within the work table <b>12</b>, for example. The work table driving circuit <b>32</b> may receive a predetermined control signal from the main controller circuit <b>23</b> in supplying the electric signal to the work table <b>12</b>. The work table <b>12</b> is allowed to move in the horizontal direction along the x-axis and z-axis based on the supplied electric signal.

An image capturing apparatus driving circuit <b>33</b> is also connected to the main controller circuit <b>23</b>. The image capturing apparatus driving circuit <b>33</b> is designed to supply a predetermined electric signal to an electric motor incorporated within the image capturing apparatus <b>21</b>, for example. The image capturing apparatus driving circuit <b>33</b> may receive a predetermined control signal from the main controller circuit <b>23</b> in supplying the electric signal to the image capturing apparatus <b>21</b>. The image capturing apparatus <b>21</b> is allowed to move in the horizontal direction along the z-axis based on the supplied electric signal.

An image processing circuit <b>34</b> is also connected to the main controller circuit <b>23</b>. The image processing circuit <b>34</b> is designed to supply a predetermined control signal to the camera unit <b>22</b>. The camera unit <b>22</b> is allowed to capture an image of the printed circuit board in response to the supply of the control signal. The image processing circuit <b>34</b> processes and analyzes the image output from the camera unit <b>22</b>. The image processing circuit <b>34</b> may receive a predetermined control signal from the main controller circuit <b>23</b> in supplying the control signal to the camera unit <b>22</b>.

As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the force sensor <b>16</b> includes a central axle <b>35</b> and an annular member <b>36</b> surrounding the central axle <b>35</b>. Connecting pieces <b>37</b> connect the central axle <b>35</b> to the annular member <b>36</b>. The connecting pieces <b>37</b> radiate from the central axle <b>35</b> in four directions, for example. A strain gauge <b>38</b> is attached on the individual connecting piece <b>37</b>.

The lower end of the central axle <b>35</b> is coupled to the upper end of the ultrasonic head <b>14</b>. The ultrasonic head <b>14</b> is detachably coupled to the central axle <b>35</b>. The annular member <b>36</b> is coupled to the lower end of the movable member <b>15</b>. A predetermined gap is defined between the upper end of the central axle <b>35</b> and the lower end of the movable member <b>15</b>. The connecting pieces <b>37</b> in this manner serve to connect the ultrasonic head <b>14</b> and the movable member <b>15</b> to each other.

Electric current is supplied to the strain gauges <b>38</b>. When the movable member <b>15</b> serves to urge the ultrasonic head <b>14</b> against a printed circuit board placed on the top surface of the work table <b>12</b>, for example, the ultrasonic head <b>14</b> lifts up the central axle <b>35</b> along the y-axis toward the movable member <b>15</b>. The central axle <b>35</b> thus receives a load. The central axle <b>35</b> moves upward relative to the annular member <b>37</b>. Strain is induced in the connecting pieces <b>37</b>. Electric resistance is correspondingly changed in the strain gauges <b>37</b>. This change in the electric resistance is converted into electric signals. The obtained electric signals are supplied from the force sensor <b>16</b> to the CPU <b>25</b> in the pressure apparatus controlling circuit <b>24</b>.

On the other hand, when the central axle <b>35</b> receives the weight of the ultrasonic head <b>14</b>, the central axle <b>35</b> falls in the y-axis toward the work table <b>12</b>. The central axle <b>35</b> moves downward relative to the annular member <b>36</b>. Strain is induced in the connecting pieces <b>37</b>. Electric resistance is correspondingly changed in the strain gauges <b>37</b>. This change in the electric resistance is converted into electric signals. The obtained electric signals are supplied from the force sensor <b>16</b> to the CPU <b>25</b> in the pressure apparatus controlling circuit <b>24</b>. Compression load and tensile load are thus detected at the force sensor <b>16</b>.

Now, assume that an electronic circuit chip is to be mounted on a printed circuit board. The printed circuit board is placed on the top surface of the work table <b>12</b>. The chip is held on the ultrasonic head <b>14</b>. Ball bumps are arranged on the lower surface of the chip. The ball bumps may be made of an electrically conductive material such as copper, for example. A position mark is printed on the lower surface of the chip. A position mark is likewise printed on the upper surface of the printed circuit board so as to identify the position of the chip. The ultrasonic head <b>14</b> is first positioned at a predetermined first position. The ultrasonic head <b>14</b> at the first position is spaced from the work table <b>12</b> at a distance.

The main controller circuit <b>23</b> then supplies the image capturing apparatus driving circuit <b>33</b> with a control signal. An electric signal is supplied to the image capturing apparatus <b>21</b> from the image capturing apparatus driving circuit <b>33</b> based on the control signal. The image capturing apparatus <b>21</b> is thus moved in the horizontal direction to a predetermined position in the z-axis toward the work table <b>12</b>. The camera unit <b>22</b> is positioned in a space between the ultrasonic head <b>14</b> and the work table <b>12</b>. The main controller circuit <b>23</b> then supplies the image processing circuit <b>34</b> with a predetermined control signal. The image processing circuit <b>35</b> outputs a control signal to the camera unit <b>22</b>. The supply of the control signal causes the camera unit <b>22</b> to simultaneously photograph the chip and the printed circuit board. The pictures or captured images are supplied to the image processing circuit <b>34</b>.

The image processing circuit <b>34</b> detects the position marks on the chip and the printed circuit board based on the captured images. The detected position is converted into a position signal. The position signal is supplied to the main controller circuit <b>23</b>. The main controller circuit <b>23</b> calculates the amount of displacement between the position marks on the chip and the printed circuit board based on the position signal. The main controller circuit <b>23</b> then calculates the adjustment amount for the work table <b>12</b> based on the amount of displacement. The main controller circuit <b>23</b> may implement a predetermined software program so as to execute the calculations.

The main controller circuit <b>23</b> supplies the work table driving circuit <b>33</b> with a control signal derived from the adjustment amount. An electric signal is thus supplied to the work table <b>12</b> from the work table driving circuit <b>33</b>. The work table <b>12</b> is allowed to move in the horizontal direction to a predetermined position. The position mark on the printed circuit board is in this manner aligned with the position mark on the chip. The chip is positioned at the target position relative to the printed circuit board. The image capturing apparatus <b>21</b> is thereafter withdrawn from the space between the ultrasonic head <b>14</b> and the work table <b>12</b>.

The main controller circuit <b>23</b> then supplies the pressure apparatus controlling circuit <b>24</b> with a control signal. The supply of the control signal causes the CPU <b>25</b> of the pressure apparatus controlling circuit <b>24</b> to implement the software program <b>28</b>. The CPU <b>25</b> supplies the voice coil motor <b>18</b> with electric current in accordance with the control parameters <b>31</b>. Here, the CPU <b>25</b> may retrieve the control parameters <b>31</b> corresponding to the ultrasonic head <b>14</b> for a temporary storage in the random access memory <b>26</b>. The perpendicular movement of the ultrasonic head <b>14</b> is controlled based on the control parameters <b>31</b>. The ultrasonic head <b>14</b> moves downward toward the work table <b>12</b>. The ultrasonic head <b>14</b> is thus positioned at a predetermined second position. The chip is spaced from the printed circuit board at a distance when the ultrasonic head <b>14</b> takes the second position.

When the ultrasonic head <b>14</b> further moves downward from the second position, the ultrasonic head <b>14</b> urges the chip against the printed circuit board. The ball bumps on the chip are forced to contact with corresponding electrically conductive pads on the printed circuit board. The electrically conductive pads may be made of an electrically conductive material such as copper, for example.

When the chip is urged against the printed circuit board, the ultrasonic head <b>14</b> lifts up the central axle <b>35</b> in the force sensor <b>16</b> along the y-axis. The central axle <b>35</b> moves upward relative to the annular member <b>36</b>. Strain is induced in the connecting pieces <b>37</b>. The strain gauges <b>38</b> get deformed, so that the electric resistance is changed. The change in the electric resistance is converted into an electric signal. The electric signal is then supplied to the CPU <b>25</b> from the force sensor <b>16</b>. The CPU <b>25</b> detects the load based on the electric signal. The CPU <b>25</b> operates to supply electric current to the voice coil motor <b>18</b> in accordance with the control parameters <b>31</b> based on the detected load. This causes the perpendicular movement of the ultrasonic head <b>14</b>. The load or thrust of the ultrasonic head <b>14</b> may be determined based on the physical property of the chip and printed circuit board.

The main controller circuit <b>23</b> supplies the ultrasonic head <b>14</b> with an electric signal. The supply of the electric signal causes the ultrasonic oscillator to generate an ultrasonic vibration. The ultrasonic vibration is transmitted to the ultrasonic head <b>14</b> in the horizontal direction. The ultrasonic vibration of the ball bumps is thus induced. Plastic deformation is induced at contacts between the ball bumps and the electrically conductive pads based on the ultrasonic energy. Oxide films are broken at the contacts between the ball bumps and the electrically conductive pads. Exchanged metallic atoms diffuse into the ball bumps and the electrically conductive pads. The ball bumps are in this manner bonded to the corresponding electrically conductive pads. A so-called ultrasonic bonding is achieved.

The CPU <b>25</b> thereafter supplies electric current to the voice coil motor <b>18</b> in accordance with the control parameters <b>31</b>. The ultrasonic head <b>14</b> thus moves upward. The ultrasonic head <b>14</b> is allowed to reach the first position through the second position. The printed circuit board is displaced from the work table <b>12</b> along with the chip. A printed circuit board and a chip are thereafter set on the work table <b>12</b> and the ultrasonic head <b>14</b> again. The chip mounter repeats the aforementioned processes. These processes are executed in three seconds, for example, after the set of the printed circuit board and chip to the accomplishment of the ultrasonic bonding.

Assume that the ultrasonic head <b>14</b> is replaced with another. The CPU <b>25</b> of the pressure apparatus controlling circuit <b>24</b> implements the software program <b>28</b>. First of all, the ultrasonic head <b>14</b> is detached from the force sensor <b>16</b>. The central axle <b>35</b> is released from the weight of the ultrasonic head <b>14</b> in the force sensor <b>16</b>. Deformation is accordingly induced in the strain gauges <b>38</b>. The resistance value subjected to a change in response to the deformation is converted into an electric signal. The electric signal is supplied to the CPU <b>25</b> from the force sensor <b>16</b>. As shown in <figref idref="DRAWINGS">FIG. 3</figref>, the CPU <b>25</b> sets the value “0” for the load of the force sensor <b>16</b> at step S<b>1</b>. The load is thus reset in the force sensor <b>16</b>.

Another ultrasonic head <b>14</b> is then attached to the force sensor <b>16</b>. The weight of this ultrasonic head <b>14</b> acts on the central axle <b>35</b> of the force sensor <b>16</b>. The central axle <b>35</b> moves downward toward the work table <b>12</b> along the y-axis. Deformation is induced in the strain gauges <b>38</b>. The resistance value subjected to a change in response to the deformation is converted into an electric signal. The electric signal is then supplied to the CPU <b>25</b> from the force sensor <b>16</b>.

The CPU <b>25</b> detects at step S<b>2</b> the load based on the received electric signal. In this case, the load corresponds to the weight of the ultrasonic head <b>14</b> after the replacement, since the load acts on the force sensor <b>16</b> solely based on the weight of the attached ultrasonic head <b>14</b>. The CPU <b>25</b> operates to refer to the head data <b>29</b> in the non-volatile memory <b>27</b>. The CPU <b>25</b> searches for the head data corresponding to the detected load. The CPU <b>25</b> in this manner operates to identify the attached ultrasonic head <b>14</b> after the replacement at step S<b>3</b>.

The CPU <b>25</b> selects at step S<b>4</b> the control parameters <b>31</b> related to the ultrasonic head <b>14</b> after the replacement. The selected control parameters <b>31</b> are set in the non-volatile memory <b>27</b>. The CPU <b>25</b> then sets the value “0” for the load of the force sensor <b>16</b> at step S<b>5</b>. The load is thus reset in the force sensor <b>16</b>. The load or thrust of the ultrasonic head <b>14</b> after the replacement can thus be detected with a higher accuracy. The chip mounter <b>11</b> thereafter returns to the normal operation. The CPU <b>25</b> may temporarily store the retrieved control parameters <b>31</b> into the random access memory <b>26</b> during the normal operation.

When the ultrasonic heads <b>14</b> are replaced in the chip mounter <b>11</b>, the load changes in the force sensor <b>16</b>. The load or weight can be related to the individual ultrasonic heads <b>14</b>, for example, so that the CPU <b>25</b> is allowed to identify the ultrasonic head <b>14</b> after replacement with a higher accuracy based on the detected load.

Moreover, the force sensor <b>16</b> is utilized to realize the identification of the ultrasonic head <b>14</b>. The force sensor <b>16</b> is originally employed in the chip mounter <b>11</b> in mounting an electronic circuit chip onto a printed circuit board. It is not necessary to add a component such as a sensor peculiar to the identification of the ultrasonic head <b>14</b> into the chip mounter <b>11</b>. The invention can be applied to a conventional chip mounter in a facilitated manner.

Furthermore, the control parameters <b>31</b> are automatically set in the chip mounter <b>11</b> in response to the identification of the ultrasonic head <b>14</b>. The operator is thus released from a troublesome operation in replacement of the ultrasonic heads <b>14</b>. Since the ultrasonic head <b>14</b> can be identified with a higher accuracy as described above, an erroneous setting of the control parameters <b>31</b> can reliably be avoided in the chip mounter <b>11</b>.

Otherwise, the reset of the load can be omitted from the aforementioned processings in the replacement of the ultrasonic heads <b>14</b>. In this case, the CPU <b>25</b> detects the weight of the ultrasonic head <b>14</b> before the replacement based on the force sensor <b>16</b>. The ultrasonic head <b>14</b> is subsequently detached from the force sensor <b>16</b>. Another ultrasonic head <b>14</b> is attached to the force sensor <b>16</b>. The weight of the ultrasonic head <b>14</b> acts on the central axle <b>35</b> of the force sensor <b>16</b>. The central axle <b>35</b> moves downward toward the work table <b>12</b> along the y-axis. Deformation is induced in the strain gauges <b>38</b>. The resistance value subjected to a change in response to the deformation is converted into an electric signal. The electric signal is supplied to the CPU <b>25</b> from the force sensor <b>16</b>.

The CPU <b>25</b> operates to detect the load based on the received electric signal. The CPU <b>25</b> calculates the difference between the detected load and the weight of the ultrasonic head <b>14</b> before the replacement at step T<b>1</b>. The CPU <b>25</b> subsequently calculates the weight of the ultrasonic head <b>14</b> after the replacement based on the derived difference at step T<b>2</b>. The CPU <b>25</b> then operates to refer to the head data <b>29</b> stored in the non-volatile memory <b>27</b>. The CPU <b>25</b> searches for the head data <b>29</b> corresponding to the detected load. The CPU <b>25</b> in this manner identifies the ultrasonic head <b>14</b> at step T<b>3</b>.

The CPU <b>25</b> selects at step T<b>4</b> the control parameters <b>31</b> related to the new ultrasonic head <b>14</b>. The selected control parameters <b>31</b> are set in the non-volatile memory <b>27</b>. The CPU <b>25</b> then sets the value “0” for the load of the force sensor <b>16</b> at step T<b>5</b>. The load is reset in the force sensor <b>16</b>. The load or thrust of the ultrasonic head <b>14</b> after the replacement can thus be detected with a higher accuracy. The chip mounter <b>11</b> thereafter returns to the normal operation. The ultrasonic head <b>14</b> after the replacement can in this manner be identified with a higher accuracy in the aforementioned manner.

The chip mounter <b>11</b> may employ a piezoelectric sensor such as a quartz pressure gage for the force sensor <b>16</b>. The working head may include a cutter and the like in addition to the ultrasonic head <b>14</b>, for example. The present invention may be applied to a cutting machine, for example. A heat source may be incorporated within the ultrasonic head <b>14</b>.